The present invention relates to steerable coated guidewires for introduction into vessels such as blood vessels to aid in placement of devices such as catheters into the vessels. Particularly, the invention relates to a process or method, and apparatus for making coated steerable guidewires having a substantially constant outer diameter and being of contiguous construction from the proximal end to the steerable and flexible distal end. Additionally the invention relates to the steerable coated guidewires produced by the method and apparatus of the invention.
Steerable guidewires which are known to the inventor hereof, required either elaborate capping procedures and apparatus for a tapered end of the wire to achieve a very flexible, but constant diameter wire, or they required the use of one or more shape memory alloy wires alone or in combination, annealed to provide steering upon heating of the wires.
An example of a known steerable guide wire for use in medical procedures which requires an elaborate capping procedure comprises a core wire of preferably stainless steel which runs the entire length of the guide wire. The distal end of the core tapers twice to an intermediate and final diameter. The distal tip of the core wire may be flattened to enhance handling and flexibility. A flat wire coil may be in contact with the first taper and is brazed at each end to the core wire. A flexible coil spring is attached to about the most distal 5 cm of the core wire. The spring is tightly wound at its proximal end and more loosely wound at its (and the core wire""s) distal end to improve flexibility at the distal tip of the guide wire. At the distal end, the coil spring and the core wire are coextensive and fixedly attached together by a hemispherical weld at the distal tip of the guide wire.
In the manufacture of known steerable guidewires, it has been necessary to manually affix a soft tip on the tapered distal end of the wire. Affixing the tip manually is very labor intensive, very costly and, because the tip is a separate part from the coating on the shaft, a degree of risk exists that the tip could fall off in use, i.e., while inside a vessel of the body.
It would be desirable to have a steerable guidewire the steering or directing of which does not require the use of heat to deform shape memory alloys. It would also be very desirable to have a steerable guide wire which does not require the distal end to be specially designed with springs or other devices and procedures to create a distal end that has a constant diameter but which is very flexible to the extent that it will conform to the direction of the vessel into which it is being inserted.
It would be desirable if a steerable guide wire could be made without excessive processes and procedures involved in the extrusion process of making the constant diameter steerable guidewire thereby potentially improving the constancy of the steerable nature of the guidewire and improving the reliability of the performance of the guidewire.
The following patents show the state of the art in the field of steerable guidewires.
The U.S. Pat. No. 5,211,183 patent to Wilson, (the ""183 patent) discloses a steerable memory alloy guide wire for use in positioning medical devices inside the body. The guide wire may be formed of any shape memory alloy or other transitional temperature activated mechanical memory materials. The guide wire is comprised in whole or in part of one or more heat activated memory alloys alone or in combination with one or more non-heat activated materials. The alloy is annealed to particular shapes (for example curves) then cooled and formed into its previously annealed shape. The invention applies the shape memory alloy concept to provide accurate steering capability to guide wires in various forms. Heating of the wire may be by induction, application of RF energy, immersion heating by water, or body temperature. If electrical current is used, the guide wire and any electrical wires may be insulated by a non-conductive sleeve or coating. The shape memory alloy may comprise all or part of a guide wire or multiple wires of memory alloy, annealed to different shapes or curves, may be bound together and used, having been annealed, for example, to work equally in opposite directions, to provide additional steering capability.
The U.S. Pat. No. 5,069,217 patent to Fleischhacker Jr. (the ""217 patent) discloses a steerable guide wire for use in medical procedures. The wire is comprised of a core wire of preferably stainless steel which runs the entire length of the guide wire. The distal end of the core tapers twice to an intermediate and final diameter. The distal tip of the core wire may be flattened to enhance handling and flexibility. A flat wire coil may be in contact with the first taper and is brazed at each end to the core wire. A flexible coil spring attached to about the most distal 5 cm of the core wire. The spring is tightly wound at its proximal end and more loosely wound at its (and the core wire""s) distal end to improve flexibility at the distal tip of the guide wire. At the distal end, the coil spring and the core wire are coextensive and fixedly attached together by a hemispherical weld at the distal tip of the guide wire. The hemispherical tip provides for smooth insertion and maneuvering of the wire. The main body of the core wire, proximal to the first taper may be coated with a polymer to improve handling characteristics. However, the most proximal end of the guide wire and the distal end with the coiled spring may be left uncoatedxe2x80x94there then results in some small net taper of the outer diameter of the guide wire as a whole from the coated portion to the uncoated tip.
The U.S. Pat. No. 5,025,799 patent to Wilson (the ""799 patent), a division of the above-mentioned Wilson U.S. Pat. No. 5,211,183 patent, the difference being the claims. The claims of this patent are directed to the guide wire being comprised of at least one solid elongated strand constructed of shape memory alloy material wherein at least one portion along the length of the strand is annealed to affect a shape change upon application of heat. The claims of the above ""183 patent are directed to a guide wire comprising at least a pair of solid elongated shape memory wire members held in substantial coaxial engagement with each other but so as to allow relative sliding movement between the two, wherein one of the wire members is annealed to under go a shape change in one direction and another is annealed to undergo a shape change in another direction, the guidewire as a whole being rotatable to enable omnidirectional steering of the guide wire.
The U.S. Pat. No. 5,800,890 patent to Cramer (the ""890 patent) discloses a steerable guide wire for catheters, which may be a combination catheter and guide wire. The guide wire is composed of a hollow metal guide tube through which liquid may flow. The guide tube is made of a plurality of tapering metal tube sections, each section tapering from proximal to distal end and each succeeding proximal end insertable into the preceding distal end and soldered together to form one tapering guide tube. Attached to the distal end of the tube is a helically wound spring, overlapping (for stability) a substantial part of the distal end of the guide tube but extending beyond the distal end of the guide tube. The distal end of the spring has a rounded cap. There is also a fine wire attached at the cap end of the spring and running to the proximal end of the spring where it is also attached to the spring. The wire provides stability and prevents the spring form being over-extended and causing damage to the vessel into which it is inserted. There may also be included a turning handle at the proximal end of the guide tube for steering and placement of the tube. There are then disclosed several applications of use of the steerable guide wire/guide tube including applications in which there is a connector, at the proximal end of the guide tube, for an injection adapter so that fluid may be injected through the guide wire/guide tube.
The U.S. Pat. No. 4,719,924 patent to Crittendon et al. (the ""924 patent) discloses a small diameter steerable guide wire with an adjustable tip. The guide wire is comprised of a tubular main wire tapering to its distal end, an outer helical outer spring attached at and extending beyond the distal end of the main wire, a distal core wire attached to the distal end of the main wire and tapering to its own distal end. The outer spring also extends beyond the distal end of the distal core wire. The outer diameter of the outer spring is approximately that of the main wire before the main wire tapers. There is a rounded cap at the end of the outer spring. There is also an inner, safety, spring extending from the distal portion of the distal core wire to the distal end of the outer springxe2x80x94where there is no wire inside the outer spring. There is a pull wire attached to the cap at the distal end of the guide wire, the pull wire extending through the lumen of the helical outer spring, and between the outer spring and the distal core wire until it reaches the joint between the main wire and the distal core wire. There is an opening in the tubular main wire through which the pull wire passes into the lumen of the main wire and out the proximal end where there is a means for retaining the pull wire in position, and for rotationally and bendably adjusting the distal tip shape and from by use of the pull wire. The wires and springs may be made of stainless steel.
The U.S. Pat. No. 4,676,249 patent to Arenal et al. (the ""249 patent) discloses an optionally bendable and flexible guide wire. The guide wire is comprised of three main components; an elongate coiled wire body having a lumen and capable of forming an arctuate shape at its distal end, a tapered curve control wire disposed inside the lumen of the coiled wire body and a stiffening member disposed inside the lumen of the coiled wire body but outside the curved control wire. The coiled wire body is composed of helically wound coils and has a curved cap on its distal end. The curved control core wire tapers towards its distal end and has a hemispherical end. The distal end of the curved control core wire is sufficiently stiff to lend rigidity to the coiled wire body. The curve control core wire is preferably made of stainless steel. The curve control wire and the stiffening member are slidable with respect to each other and with respect to the coiled wire body. The coiled wire body is preferably plastic-coated stainless steel.
The U.S. Pat. No. 4,068,615 patent to LeNir (the ""615 patent) discloses a digital computer control for a wire coating line primarily directed at insulated electrical wires. The speed of the wire passing through a conventional extruder is controllable, the rate and temperature of the extruded plastic coating are controlled, and the distance of the cooling means from the coating means is controllable. These controllable factors affect both the capacitance and diameter of the coated wire produced. The capacitance or diameter of the coated wire is measured, provided as a digital value to a control computer which compares the received value to a control valve and then the operating characteristics of the line are altered to provide wire of the desired capacitance or diameter. There is an extruder screw, the RPM of which may be controlled in response to either measured versus control capacitance or diameter of the extruded wire. The application of the control system is mainly to plastic coated insulated electrical wires. The control process seems to be able to vary the thickness of the plastic coating slightly to achieve a uniform outer diameter on an essentially uniform diameter inner wire.
The U.S. Pat. No. 3,893,642 patent to Van Vlaenderen (the ""642 patent) is a Continuation-in-Part of an abandoned application and discloses polyethylene terephthalate plastic coated wire for use primarily in the manufacture of barbed wire, wire mesh, wire netting, wire fences and the like. The disclosure of the process of making the wire is essentially the same as the related ""545 patent discussed below. The process produces wire with polyethylene terephthalate plastic coating which is at least 95% up to 98% amorphous. The process produces a rather large diameter wire which is not used in delicate medical applications. The U.S. Pat. No. 3,829,545 patent to Van Vlaenderen (the ""545 patent) discloses essentially the same process and produces essentially the same products as the above ""642 patent. In a preferred embodiment of this invention, a heated wire is passed through an extrusion head in which molten plastic is extruded under pressure to form a coating on the wire to produce coated wire. The wire is preheated by any conventional technique, for example electrical heating. The wire is continuously passed from a storage spool to a heater and then to the extrusion head of the extrusion machine. The operation is continuous, and the preheating of the wire is on a continuous basis. There is an Archimedes screw in a heated cylinder in the extrusion machine through which plastic grains pass and become more and more plastically deformable. The heated plastic is pushed forward while being increasingly compressed. The thickness of the plastic coatings on the wire may be regulated by using differently sized extrusion heads as well as controlling the pressure produced by the Archimedes screw. Immediately after extrusion, the plastic coated wire is chilled, preferably by cold water to maintain a plastic coated steel wire of which the coating is preferably at least 80% amorphous. The coating has a thickness of about 0.1 to 0.3 mm, and the invention is particularly applicable to metal wires having a diameter greater than 1.0 mm. The claims are directed to an improved process for manufacturing the wire.
The most basic embodiment of the present invention discloses a constant diameter coated steerable guidewire and a method and apparatus to produce the steerable guidewire. The invention provides an inner wire member which tapersxe2x80x94preferably linearlyxe2x80x94over a minor segment or portion of the inner wire member where the linearly tapered minor segment is located at least one end of the inner wire member. A coating is applied to the wire wherein the outer diameter of the coated wire remains constant despite the taper of the inner wire member. The amount of coating is increased proportionately as the diameter of the inner wire member decreases so that the resulting steerable guidewire has a constant outer diameter. Thus the flexibility and steerability of the resulting steerable guidewire is increased by tapering the inner wire member, but the finished coated wire maintains a constant outer diameter.
One embodiment of the present invention provides a coated steerable guidewire comprising an inner wire member having a constant outer diameter over a major segment of the inner wire member and a tapered (preferably linearly tapered) outer diameter over a minor segment of the wire member, the minor segment located at one end of the inner wire member; and a coating adhered to the inner wire member, the coating having a constant outer diameter such that the resulting coated steerable guidewire has a constant outer diameter.
There is also provided a method for producing a constant outer diameter coated steerable guidewire comprising the steps of advancing wire having at least one end with a linearly tapering outer diameter, through an extrusion device having a cross head/extrusion head; detecting an outer diameter of the wire as it passes into the cross head; depositing molten coating material on the wire as the wire passes through the cross head thereby producing a coated wire; cooling the coated wire; hauling off the coated wire; and controlling the advancing and depositing with a programmable microprocessor such that the constant outer diameter coated steerable guidewire is produced. The programmable microprocessor is controlled by software code which causes the microprocessor to slow the rate of feed and haul-off of the wire through the cross head when a decrease in outer diameter of the wire is detected, such that more coating is deposited as the outer diameter of the wire decreases so that the resulting coated wire has a constant outer diameter.
Another embodiment of the present invention is an apparatus for producing coated steerable guidewire of constant outer diameter comprising a programmable microprocessor which provides control signals to an extrusion apparatus having a controllable means for advancing wire through the extrusion apparatus, the extrusion apparatus comprising; a cross head/extrusion head through which the wire passes; a detecting device for detecting outer diameter of the wire as the wire passes into the cross head and for providing signals to the programmable microprocessor; at least one coating apparatus which provides molten coating material into the cross head to coat the wire as the wire passes through the cross head; a cooling means which cools the wire coated with the coating material after the wire passes out of the cross head; and a haul-off device for removing the wire from the cooling means, thereby producing the coated flexible guidewire. The wire has at least one end thereof having a linearly decreasing outer diameter decreasing from Dmax to Dmin over a linearly tapering portion of length Lt of the wire. The detecting device detects the linearly decreasing outer diameter of the wire, and the detecting device is preferably a laser monitor. The microprocessor controls a rate at which the extrusion apparatus advances the wire in response to the signals provided by the detection device wherein the rate is decreased by the microprocessor as the outer diameter of the wire decreases, and a thickness of the coating material is thereby increased such that the coated steerable guidewire has a constant outer diameter.
In yet another embodiment, there is provided a constant outer diameter coated steerable guidewire produced by a process comprising the steps of advancing wire having at least one end with a linearly tapering outer diameter, through an extrusion device having a cross head/extrusion head; detecting an outer diameter of the wire as it passes into the cross head; depositing molten coating material on the wire as the wire passes through the cross head thereby producing a coated wire; cooling the coated wire; hauling off the coated wire; and controlling the advancing and depositing with a programmable microprocessor thereby producing the constant outer diameter coated steerable guidewire.
An aspect of the present invention is to provide a coated steerable guidewire which has a tapered inner wire member and a constant outer diameter.
Another aspect of the invention is to provide a method for producing a constant outer diameter coated steerable guidewire which has a tapered inner wire member.
Yet another aspect of the invention is to provide a steerable guidewire which does not require elaborate capping or tipping to achieve flexibility and steerability while maintaining a constant outer diameter of the guidewire.
Still another aspect of the invention is to provide a steerable guidewire made from xe2x80x9csimplexe2x80x9d starting materials which do not require special annealing procedures to produce steering capability and which do not require heating of the wire during insertion into body vessels such as blood vessels to achieve steerability.
These and further objects of the present invention will become apparent to those skilled in the art after a study of the present disclosure of the invention and with reference to the accompanying drawings which are a part hereof, wherein like numerals refer to like parts throughout, and in which: